Current radar systems, including automotive radar systems, often require wide angle coverage having narrow beams and a high update rate, all in a small package size. As an example, current automotive radar systems for applications including collision warning, pre-crash sensing and adaptive cruise control incorporate a fixed beam, switched beam or mechanically scanned antenna that have limited performance by falling short of these requirements. In the case of mechanically scanned antennas, the update rate is too slow for current demands, system size and cost are high, and reliability is low.
Allowing an antenna to electronically scan has benefits over a mechanically scanned antenna, including fast scanning, the ability to host multiple antenna beams on the same array, eliminating mechanical complexity and reliability issues, the ability to angle the antenna in such a way that it reduces radar cross section and the ability to operate over a wider frequency range, a wide field of view, a range of beamwidths and a high update rate.
Electronically scanned antennas have broad applicability for both commercial and military applications, including advanced radar systems, cellular base stations, satellite communications, and automotive anti-collision radar. However, conventional electronically scanned antennas using discrete phase shifters are expensive and introduce excessive RF loss at typical automotive radar frequencies (i.e., 24 GHz and 76 GHz). Contemporary systems individually assemble, package, individually mount and individually test discrete phase shifters on an antenna structure. Typically, ten to hundreds of phase shifters are mounted on a scanning antenna. In military applications, several hundred phase shifters are commonly mounted on a scanning antenna.
Electronically scanned antennas have been utilized since electronically controlled phase shifters were employed. Phase shifters allow an antenna beam to be steered in a desired direction without physically repositioning the antenna. Phase shifters are critical elements for electronically scanned phase array antennas, and typically represent a significant amount of the cost of producing an antenna array. Phase shifters can represent nearly half of the cost of the entire electronically scanned array. This considerable cost has limited the deployment of electronically scanned antennas and has largely curbed their use to military systems and a limited number of commercial applications such as cellular telephone base stations. The application of these technologies to consumer systems is prohibitive due to fabrication costs. Phase shifters are manufactured by standard manufacturing processes and include switch based and continuously variable phase shifters such as Gallium-Arsenide (GaAs) based varactors, GaAs FETs, switched delay lines or high/low pass filter structures using PIN diodes or FET switches, ferromagnetic systems, and Micro-electrical mechanical system (MEM) varactors and switches. There is a significant demand, especially in the wireless and microwave industries, for affordable phase shifters that can reduce the cost of an electronically scanned antenna system and allow them to be deployed more widely.